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# multiAgents.py # -------------- # Licensing Information: You are free to use or extend these projects for # educational purposes provided that (1) you do not distribute or publish # solutions, (2) you retain this notice, and (3) you provide clear # attribution to UC Berkeley, including a link to http://ai.berkeley.edu. # # Attribution Information: The Pacman AI projects were developed at UC Berkeley. # The core projects and autograders were primarily created by John DeNero # (denero@cs.berkeley.edu) and Dan Klein (klein@cs.berkeley.edu). # Student side autograding was added by Brad Miller, Nick Hay, and # Pieter Abbeel (pabbeel@cs.berkeley.edu). from util import manhattanDistance from game import Directions import random, util from game import Agent class ReflexAgent(Agent): """ A reflex agent chooses an action at each choice point by examining its alternatives via a state evaluation function. The code below is provided as a guide. You are welcome to change it in any way you see fit, so long as you don't touch our method headers. """ def getAction(self, gameState): """ You do not need to change this method, but you're welcome to. getAction chooses among the best options according to the evaluation function. Just like in the previous project, getAction takes a GameState and returns some Directions.X for some X in the set {NORTH, SOUTH, WEST, EAST, STOP} """ # Collect legal moves and successor states legalMoves = gameState.getLegalActions() # Choose one of the best actions scores = [self.evaluationFunction(gameState, action) for action in legalMoves] bestScore = max(scores) bestIndices = [index for index in range(len(scores)) if scores[index] == bestScore] chosenIndex = random.choice(bestIndices) # Pick randomly among the best "Add more of your code here if you want to" return legalMoves[chosenIndex] def evaluationFunction(self, currentGameState, action): """ Design a better evaluation function here. The evaluation function takes in the current and proposed successor GameStates (pacman.py) and returns a number, where higher numbers are better. The code below extracts some useful information from the state, like the remaining food (newFood) and Pacman position after moving (newPos). newScaredTimes holds the number of moves that each ghost will remain scared because of Pacman having eaten a power pellet. Print out these variables to see what you're getting, then combine them to create a masterful evaluation function. """ # Useful information you can extract from a GameState (pacman.py) successorGameState = currentGameState.generatePacmanSuccessor(action) newPos = successorGameState.getPacmanPosition() newFood = successorGameState.getFood() newGhostStates = successorGameState.getGhostStates() newScaredTimes = [ghostState.scaredTimer for ghostState in newGhostStates] "*** YOUR CODE HERE ***" closestFoodDistance, closestGhostDistance = 1e9, 1e9 foodDistances, ghostDistances = [closestFoodDistance], [closestGhostDistance] foodList = newFood.asList() currentFoodNumber = len(currentGameState.getFood().asList()) for food in foodList: foodDistances.append(util.manhattanDistance(newPos, food)) closestFoodDistance = min(foodDistances) for ghost in newGhostStates: ghostDistances.append(util.manhattanDistance(newPos, ghost.getPosition())) closestGhostDistance = min(ghostDistances) foodDiff = currentFoodNumber - len(foodList) evalScore = 1/(closestFoodDistance + 1) if closestGhostDistance <= 1: return -1e9 elif foodDiff > 0: return 1e9 else: return evalScore def scoreEvaluationFunction(currentGameState): """ This default evaluation function just returns the score of the state. The score is the same one displayed in the Pacman GUI. This evaluation function is meant for use with adversarial search agents (not reflex agents). """ return currentGameState.getScore() class MultiAgentSearchAgent(Agent): """ This class provides some common elements to all of your multi-agent searchers. Any methods defined here will be available to the MinimaxPacmanAgent, AlphaBetaPacmanAgent & ExpectimaxPacmanAgent. You *do not* need to make any changes here, but you can if you want to add functionality to all your adversarial search agents. Please do not remove anything, however. Note: this is an abstract class: one that should not be instantiated. It's only partially specified, and designed to be extended. Agent (game.py) is another abstract class. """ def __init__(self, evalFn = 'scoreEvaluationFunction', depth = '2'): self.index = 0 # Pacman is always agent index 0 self.evaluationFunction = util.lookup(evalFn, globals()) self.depth = int(depth) class MinimaxAgent(MultiAgentSearchAgent): """ Your minimax agent (question 2) """ def getAction(self, gameState): """ Returns the minimax action from the current gameState using self.depth and self.evaluationFunction. Here are some method calls that might be useful when implementing minimax. gameState.getLegalActions(agentIndex): Returns a list of legal actions for an agent agentIndex=0 means Pacman, ghosts are >= 1 gameState.generateSuccessor(agentIndex, action): Returns the successor game state after an agent takes an action gameState.getNumAgents(): Returns the total number of agents in the game gameState.isWin(): Returns whether or not the game state is a winning state gameState.isLose(): Returns whether or not the game state is a losing state """ "*** YOUR CODE HERE ***" # util.raiseNotDefined() return self.value(gameState, 0, self.depth)[1] def value(self, gameState, agentIndex, depth): if gameState.isWin() or gameState.isLose() or depth == 0: return self.evaluationFunction(gameState), Directions.STOP elif agentIndex == 0: return self.maxValue(gameState, agentIndex, depth) else: return self.minValue(gameState, agentIndex, depth) def minValue(self, gameState, agentIndex, depth): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) selectedScore, selectedAction = 1e9, Directions.STOP for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth)[0] if successorScore < selectedScore: selectedScore = successorScore selectedAction = action return selectedScore, selectedAction def maxValue(self, gameState, agentIndex, depth): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) selectedScore, selectedAction = -1e9, Directions.STOP for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth)[0] if successorScore > selectedScore: selectedScore = successorScore selectedAction = action return selectedScore, selectedAction class AlphaBetaAgent(MultiAgentSearchAgent): """ Your minimax agent with alpha-beta pruning (question 3) """ def getAction(self, gameState): """ Returns the minimax action using self.depth and self.evaluationFunction """ "*** YOUR CODE HERE ***" # util.raiseNotDefined() return self.value(gameState, 0, self.depth, -1e9, 1e9)[1] def value(self, gameState, agentIndex, depth, alpha, beta): if gameState.isWin() or gameState.isLose() or depth == 0: return self.evaluationFunction(gameState), Directions.STOP elif agentIndex == 0: return self.maxValue(gameState, agentIndex, depth, alpha, beta) else: return self.minValue(gameState, agentIndex, depth, alpha, beta) def minValue(self, gameState, agentIndex, depth, alpha, beta): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) selectedScore, selectedAction = 1e9, Directions.STOP for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth, alpha, beta)[0] if successorScore < selectedScore: selectedScore = successorScore selectedAction = action if selectedScore < alpha: return selectedScore, selectedAction beta = min(beta, selectedScore) return selectedScore, selectedAction def maxValue(self, gameState, agentIndex, depth, alpha, beta): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) selectedScore, selectedAction = -1e9, Directions.STOP for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth, alpha, beta)[0] if successorScore > selectedScore: selectedScore = successorScore selectedAction = action if selectedScore > beta: return selectedScore, selectedAction alpha = max(alpha, selectedScore) return selectedScore, selectedAction class ExpectimaxAgent(MultiAgentSearchAgent): """ Your expectimax agent (question 4) """ def getAction(self, gameState): """ Returns the expectimax action using self.depth and self.evaluationFunction All ghosts should be modeled as choosing uniformly at random from their legal moves. """ "*** YOUR CODE HERE ***" # util.raiseNotDefined() return self.value(gameState, 0, self.depth)[1] def value(self, gameState, agentIndex, depth): if gameState.isWin() or gameState.isLose() or depth == 0: return self.evaluationFunction(gameState), Directions.STOP elif agentIndex == 0: return self.maxValue(gameState, agentIndex, depth) else: return self.expValue(gameState, agentIndex, depth) def expValue(self, gameState, agentIndex, depth): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) # selectedScore, selectedAction = 1e9, Directions.STOP expectedValue, prob = 0, 0 for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth)[0] prob = 1/len(actionList) expectedValue = expectedValue + prob * successorScore # formula of expected value return expectedValue, random.choice(actionList) def maxValue(self, gameState, agentIndex, depth): nextAgent = (agentIndex + 1) % gameState.getNumAgents() if nextAgent == 0: nextDepth = depth - 1 else: nextDepth = depth actionList = gameState.getLegalActions(agentIndex) selectedScore, selectedAction = -1e9, Directions.STOP for action in actionList: successorGameState = gameState.generateSuccessor(agentIndex, action) successorScore = self.value(successorGameState, nextAgent, nextDepth)[0] if successorScore > selectedScore: selectedScore = successorScore selectedAction = action return selectedScore, selectedAction def betterEvaluationFunction(currentGameState): """ Your extreme ghost-hunting, pellet-nabbing, food-gobbling, unstoppable evaluation function (question 5). DESCRIPTION: <write something here so we know what you did> """ "*** YOUR CODE HERE ***" # util.raiseNotDefined() if currentGameState.isWin(): return 1e9 elif currentGameState.isLose(): return -1e9 currPos = currentGameState.getPacmanPosition() currFood = currentGameState.getFood() currGhostStates = currentGameState.getGhostStates() currScore = currentGameState.getScore() currCapsList = currentGameState.getCapsules() currFoodList = currFood.asList() closestFoodDistance, closestGhostDistance, closestCapsuleDistance = 1e9, 1e9, 1e9 foodDistances, ghostDistances, capsuleDistances = [closestFoodDistance], [closestGhostDistance], [closestCapsuleDistance] foodCoeff = 1 capsuleCoeff = 1 scoreCoeff = 1 ghostDistCoeff = 2 scaredGhostTimer = 4 # closest food for food in currFoodList: foodDistances.append(util.manhattanDistance(currPos, food)) closestFoodDistance = min(foodDistances) # closest capsule for capsule in currCapsList: capsuleDistances.append(util.manhattanDistance(currPos, capsule)) closestCapsuleDistance = min(capsuleDistances) # dealing with ghost for ghost in currGhostStates: ghostDistance = util.manhattanDistance(currPos, ghost.getPosition()) if ghostDistance <= ghostDistCoeff and ghost.scaredTimer > scaredGhostTimer: return 1e9 elif ghostDistance <= ghostDistCoeff and ghost.scaredTimer <= scaredGhostTimer: return -1e9 evalScore = foodCoeff * (1/(closestFoodDistance + 1)) + capsuleCoeff * 1/(closestCapsuleDistance + 1) + scoreCoeff * currScore return evalScore # Abbreviation better = betterEvaluationFunction
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